Understanding the manner in which the fetal period provides the substrate for human development and postnatal function is at the core of developmental inquiry. After 10 years of investigation, our orientation is that fetal neurobehavioral development reflects maturation of the central nervous system during gestation and establishes the origins of individual differences in autonomic functioning. The goals of our proposed and past research are threefold: to develop ways of measuring fetal neurobehavior and apply these over gestation to document development of healthy fetuses (Ontogeny); to evaluate the continuity of function from the prenatal to postnatal periods (Prediction); and to determine whether and how maternal mediators affect the course of antenatal development (Maternal Influences). Two studies are proposed which build on our prior results and extend us into new theoretical and methodological domains. The first will investigate the effects of evoked maternal arousal and relaxation on fetal neurobehavior, as well as examine the role of maternal attributes associated with psychological well-being and stress buffering on observed effects. 106 maternal-fetal pairs will be monitored twice during 24 and 36 weeks gestation. Fetal (heart rate, movement, and their interrelation) and maternal (skin conductance, respiration, heart rate, blood pressure) will be collected simultaneously, and digitized using an automated system. Doppler velocimetry will be used to assess umbilical and uterine blood flow. Postnatal data, relating infant regulatory and reactive processes to patterns of maternal and fetal prenatal responses, will be collected at 6 weeks and 16 months. The second study will investigate the ontogeny of fetal neurobehavioral measures, as described above, during a gestational period that represents a transition in neurobehavioral development. A total of 105 fetuses will be assessed every 3 weeks from 24 through 38 weeks gestation. To provide data points at weekly intervals, onset of data collection will be staggered among individuals. Positive maternal psychosocial attributes will also be evaluated in relation to ontogeny. Maturation and neurologic optimality will be assessed in the neonatal period. Growth curve modeling and time series analyses will be applied to evaluate whether rate of development during gestation predicts physical, neurological, and regulatory maturation at birth.